The basic idea is that if you drag the tip of a butter knife through the surface of your icing, letting the knife go approximately an inch deep, you want the surface of the icing to smoothe over again in approximately 10 seconds. If it takes longer, the icing is too thick. Slowly add more water. If your icing surface smoothes over in less than 5-10 seconds, it is too runny. Mix your icing longer or slowly add more sifted icing sugar (confectioner's sugar) to thicken it.

Step 3: Outlining and Flooding the Cookie

Once you have your cookies baked and icing made, it’s time to begin by piping your outline. I like to use a piping bag fitted with a coupler and #3 tip. Fill or flood your cookie with white royal icing right away. You could leave the outline to set to create a solid dam, but you’ll be able to see the border when the icing dries.

Here is a video to show you how to outline and flood a cookie with icing:

Step 4: 2nd Layer of Icing

Using a #3 tip and your black icing, pipe a dot and then a spiral, starting at the center of the cookie. Shake the cookie gently to help the black merge into the white icing.